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DM500V8多媒体卫星接收机电源外置,主机采用12V电源供电,LNB供电电路以LT1930为核心元件,与其他直流供电机种的LNB供电电路相比有本质区别。一般直流供电数字机的LNB供电电路多采用双极性DC-DC转换集成电路34063和外围电路组成升压电路,通过改变取样电阻阻值输出13/18V极化电压,而DM500V8机LNB供电电路由高功率开关稳压器LT1930与外围电路组成,通过主芯片STB02500输出不同脉宽PWM信号控制LNB供电电路输出13/18V极化电压。如图为DM500V8多媒体卫星接收机LNB供电电路原理图,下面简要分析其工作原理与故障检修。
DM500V8 multimedia satellite receiver external power supply, the host uses 12V power supply, LNB power supply circuit to LT1930 as the core components, and other types of DC power supply LNB power supply circuit is essentially different. General LVD power supply DC digital power supply circuit using bipolar DC-DC converter IC 34063 and the peripheral circuit to form a boost circuit, by changing the sampling resistor output 13 / 18V polarization voltage, and DM500V8 LNB power supply circuit by High-power switching regulator LT1930 and peripheral circuits, the main chip STB02500 output PWM signal of different pulse width control LNB power supply circuit output 13 / 18V polarization voltage. The picture shows the DM500V8 multimedia satellite receiver LNB power supply circuit schematic, the following brief analysis of its working principle and troubleshooting.